The Department of Justice and the Environmental Protection Agency announced on Thursday a $5.15 billion settlement with a subsidiary of Anadarko Petroleum in what is, according to the two agencies, the largest pollution cleanup settlement in history.

The Obama administration proposed a long-awaited rule on Tuesday to clarify that the Clean Water Act protects wetlands near rivers and waterways fed by seasonal thaws and rains — a decision that could particularly shield water sources in the West.

Gina McCarthy was deep in enemy territory. Here on this wind-whipped prairie pocked with strip mines, Ms. McCarthy, the administrator of the Environmental Protection Agency, faced 20 coal miners, union workers and local politicians deeply suspicious of the new climate change regulations she had come to pitch.